A dampening unit is known from U.S. Pat. No. 3,168,037. Either a fountain roller, which takes up the dampening agent from a dampening agent reservoir, or a transfer roller which is rolling off on the fountain roller, are driven by a controllable drive mechanism in such a way that a rotating speed of these two rollers can be changed. However, the magnitude of the rotating speed of these two rollers is always identical.
A dampening unit is known from U.S. Pat. No. 3,986,452. A fountain roller, taking up a dampening agent from a dampening agent reservoir, and at least one further roller, which is in roller-to-roller contact with the fountain roller, have controllable drive mechanisms, each of which drive mechanisms is independent of the other. This further roller is in a roller-to-roller contact with a dampening agent application roller that is placed against a forme cylinder. A traversing bridge roller is placed against the dampening agent application roller.
A dampening unit, with a fountain roller taking up a dampening agent from a dampening agent reservoir and with a slip roller rolling off on the fountain roller, is known from EP 0 893 251 A2. Both rollers can be driven by separate drive mechanisms, if required. Both rollers always have the same surface speed.
A film-type dampening unit for rotary printing presses is known from EP 0 462 490 A1. In a roller train extending from a dampening agent tank as far as the forme cylinder and consisting of three or four rollers, a fountain roller and a metering roller are driven together by a first electric motor. A dampening agent distribution roller following the metering roller in the roller train is additionally moved axially back and forth by a mechanism. A bridge roller is placed against a dampening agent application roller which is placed against the dampening agent distribution roller and the forme cylinder.
A dampening unit of an offset rotary printing press is known from DE 29 32 105 C2. The dampening unit has a roller train, consisting of three rollers, extending from the dampening agent pick-up up to the forme cylinder. Each one of the three rollers is driven independently of each other by a controllable electric motor, each of which controllable electric motor preferably can be set in an infinitely variable manner.
A drive mechanism for the dampening unit of an offset printing press is known from DE 38 32 527 C2. A traversing bridge roller is provided, which is simultaneously placed against a dampening agent application roller and an ink application roller. The bridge roller is pneumatically driven. Its number of revolutions is controlled by changing the pneumatic pressure.
A dampening unit for a printing press is known from DE 299 00 216 U1. A first roller, which takes up a dampening agent, and a second roller, which is connected with the first roller for transferring dampening agent, are provided. Both of these rollers are rotatably driven. A slippage between the two rollers exists, which slippage can be set by a control device when the dampening unit is operated.
Drive mechanisms for a printing group are known from WO 03/039873 A1. The rotatory driving device and the traversing driving device of a roller are arranged on opposite ends of the roller.
A dampening unit of an offset rotary printing press is known from JP-A-01 232 045. The dampening unit has a roller train consisting of three rollers that are positioned extending from the dampening agent pick-up up to the forme cylinder. The fountain roller, which is the first roller, as well as the transfer roller which is the second roller are driven independently of each other, each by a controllable motor.